Mature human relaxin is a hormonal peptide of approximately 6000 daltons known to be responsible for remodelling the reproductive tract before parturition, thus facilitating the birth process. This protein appears to modulate the restructuring of connective tissues in target organs to obtain the required changes in organ structure during pregnancy and parturition. See, Hisaw, F. L., Proc. Soc. Exp. Biol. Med., 23: 661-663 (1926); Schwabe, C., et al., Biochem. Biophys. Res. Comm., 75: 503-570 (1977); James, R. et al., Nature, 267: 544-546 (1977). A concise review of relaxin was provided by Sherwood, D. in The Physiology of Reproduction, Chapter 16, "Relaxin", Knobil, E. and Neill, J., et al. (eds.), (Raven Press Ltd., New York), pp. 585-673 (1988). Circulating levels of relaxin are elevated for the entire nine months of pregnancy and drop quickly following delivery.
While predominantly a hormone of pregnancy, relaxin has also been detected in the non-pregnant female as well as in the male. Bryant-Greenwood, G. D., Endocrine Reviews, 3: 62-90 (1982) and Weiss, G., Ann. Rev. Physiol., 46:43-52 (1984).
Relaxin has been purified from a variety of species including porcine, murine, equine, shark, tiger, rat, dogfish and human, and shows at least primary and secondary structural homology to insulin and the insulin-like growth factor. In the human, relaxin is found in most abundance in the corpora lutea (CL) of pregnancy. However, specific nuclei in the brain have relaxin receptors and other nuclei contain messenger RNA for relaxin. Several nuclei with cells bearing relaxin receptors are found in the area of the hypothalamus.
Two human gene forms have been identified, (H1) and (H2). Hudson, P., et al., Nature, 301: 628-631 (1983); Hudson, P., et al., The EMBO Journal, 3: 2333-2339 (1984); and U.S. Pat. Nos. 4,758,516 and 4,871,670. Only one of the gene forms (H2) has been found to be transcribed in CL. It remains unclear whether the (H1) form is expressed at another tissue site, or whether it represents a pseudo-gene. When synthetic human relaxin (H2) and certain human relaxin analogs were tested for biological activity, the tests revealed a relaxin core necessary for biological activity as well as certain amino acid substitutions for methionine that did not affect biological activity. Johnston, et al., in Peptides: Structure and Function, Proc. Ninth American Peptide Symposium, Deber, C. M., et al. (eds.) (Pierce Chem. Co. 1985).
Methods of making relaxin are also described in U.S. Pat. No. 4,835,251 and in co-pending U.S. Ser. Nos. 07/908,766 (PCT US90/02085) and 08/080,354 (PCT US94/0699). Methods of using relaxin in cardiovascular therapy and in the treatment of neurodegenerative diseases are described in U.S. Pat. No. 5,166,191 and in U.S. Ser. No. 07/902,637 (PCT US92/06927). Certain formulations of human relaxin are described in allowed U.S. Ser. No. 08/050,745.
Recombinant human relaxin (H2) in currently in Phase I human clinical trials in scleroderma patients. Scleroderma is a disease involving an imbalance in tissue reformation giving rise to the overproduction of collagen, and ultimately resulting in swelling and hardening of the skin (and affected organs).
Vascular Endothelial Growth Factor (VEGF) has also been localized in situ in the corpus luteum (CL) of pregnancy, as well as the placenta and the endometrium. See Sharkey et al., J. Reprod. Fert. 99:609-615 (1993); Li et al. Growth Factors 22:277-282 (1994); Phillips et al. Endocrinology 127:965-967 (1990). VEGF, highly conserved glycoprotein secreted by macrophages, exhibits a potent ability to induce new vessel growth in vivo. VEGF is mitogen specific for endothelial cells and can induce both endothelial cell migration and serine and metalloproteinase expression (for review, see Thomas, K. A., J. Biol. Chem. 271:603-606 (1996). The strongest sites of VEGF expression are the fetal and maternal macrophages. Besides its proposed role in promoting new vessel growth during pregnancy, VEGF has also been proposed to be involved in persistent and dysregulated vessel growth in pathological conditions such as tumor metastasis, diabetic retinopathy, and rheumatoid arthritis.